1. Field of the Invention
This invention relates to a discharge recovery method for an ink jet recording head provided with discharge recovery means for recovering unsatisfactory discharge of ink from the discharge openings of the ink jet recording head.
2. Related Background Art
An ink jet recording apparatus is such that ink is supplied into a recording head, a drive element provided correspondingly to at least one ink discharge opening formed in the front surface of the recording head is driven on the basis of a recording,.data signal to thereby cause the ink to be discharged through the ink discharge opening and form a flying liquid droplet toward a recording medium. Such liquid droplet is caused to adhere to the recording medium to thereby accomplish recording.
In the recording head of the ink jet recording apparatus of this type, unsatisfactory discharge is caused by the entry of air into a liquid path communicating with the ink discharge opening or the adherence of paper dregs or viscosity-increased ink in the liquid path. In order to eliminate such unsatisfactory discharge and achieve the stability of discharge, as shown, for example, in U.S. Pat. No. 4,600,931 issued to Terasawa and U.S. Pat. No. 4,123,761 issued to Kimura, a gear pump or the like has been provided in an ink supply path communicating with the recording head and supplying ink to thereby forcibly pressurize the ink and cause the air and foreign materials in the liquid path to be discharged. In addition a pump mechanism or the like for sucking air and foreign materials from the discharge opening by negative pressure and causing them to be discharged has been provided.
However, in the conventional recovery method for an ink jet recording head, it is necessary to discharge a great deal of ink to eliminate the air slightly stagnating in the liquid path or the viscosity-increased ink in the discharge opening and the liquid path. Also, much time is required for operating these drive systems (the pump, etc.) and as a result, it is necessary to stop recording temporarily, thus inefficiently wasting time.
Also, discretely from the above-described construction, a construction in which a drive element such as a piezoelectric element for discharge is driven during non-recording to thereby effect predischarge, as described, for example, in U.S. Pat. No. 3,925,788 issued to Kashio, U.S. Pat. No. 3,925,789 issued to Kashio, U.S. Pat. No. 4,183,030 issued to Kaieda et al., and U.S. Pat. No. 4,176,363 issued to Kasahara has been proposed
However, in the above-described construction wherein pre-discharge is effected, the drive element used for recording is used also as the drive element for pre-discharge, and there have been technical tasks left to be solved in the points which will be described later.
In the pre-discharge of the above-described construction, the drive element is used for both purposes, and this is effective in the prevention of clogging or unsatisfactory discharge. But when unsatisfactory discharge has already occurred as may occur when recording is again effected from a long time of unused state, the effect of releasing is unsatisfactory.
Also, a construction in which the pre-discharge of the above-described construction is effected with the driving conditions or the like changed is shown, for example, in U.S. Pat. No. 4,466,005 issued to Yoshimura. However, in the construction described above in detail, there have been left the technical tasks that in the sense that the drive element is used for both purposes, there are cases where discharge recovery cannot be completely accomplished, and the technique which is effective because of a piezo-electric element being used as the drive element cannot be simply applied to a construction in which heat energy generating means generating heat energy is used as an element generating energy used for the discharge of ink.